The ability to accurately predict the shift in the reference temperature (RTNDT) and the decrease in the Charpy upper-shelf energy (CvUSE) for reactor pressure vessel materials is essential to the evaluation of the structural integrity of reactor pressure vessels, and is an important parameter for developing the operating limitations of the reactor pressure vessel. Furthermore, 10CFR50, Appendix G, requires that the material upper-shelf energy be monitored and appropriate action be taken before the upper-shelf reaches 50 ft-lb (67.8 J) as a result of fast neutron radiation-induced damage.

The submerged-arc weld metals, made with copper-plated wire and Linde 80 flux, are of importance because of their high sensitivity to radiation damage. The availability of significant new data to the data base from reactor vessel material surveillance capsules provides an expanded data base of sufficient quantity from which improved prediction correlations could be developed.

Updating techniques for predicting the decrease in Charpy upper shelf energy concurrently with the development of an improved correlation for the shift in RTNDT was performed. Developing prediction correlations for both the shift in RTNDT and the decrease in CvUSE distinctly representative of the behavior of Linde 80 submerged arc weld metal were possible. By revising the correlation to address only the fluence range of interest, the standard deviation of the shift correlation was reduced. The technique for drop in upper shelf energy did not reflect a similar improvement suggesting lack of understanding of the mechanistic modeling.